Mechanical robustness of HL-LHC collimator designs

F Carra,E Skordis,G Gobbi,A Bertarelli,S Redaelli,J Guardia-Valenzuela,F Harden,M Guinchard,M Pasquali

doi:10.1088/1742-6596/1350/1/012083

Abstract

Two new absorbing materials were developed as collimator inserts to fulfil the requirements of HL-LHC higher brightness beams: molybdenum-carbide graphite (MoGr) and copper-diamond (CuCD). These materials were tested under intense beam impacts at CERN HiRadMat facility in 2015, when full jaw prototypes were irradiated. Additional tests in HiRadMat were performed in 2017 on another series of material samples, including also improved grades of MoGr and CuCD, and different coating solutions. This paper summarizes the main results of the two experiments, with a main focus on the behaviour of the novel composite blocks, the metallic housing, as well as the cooling circuit. The experimental campaign confirmed the final choice for the materials and the design solutions for HL-LHC collimators, and constituted a unique chance of benchmarking numerical models. In particular, the tests validated the selection of MoGr for primary and secondary collimators, and CuCD as a valid solution for robust tertiary collimators.

Highlights

A novel design was proposed for LHC collimators [1], to cope with the requirements imposed by the High-Luminosity upgrade of the LHC (HL-LHC)
The second experiment, “Multimat” [9], featured several material samples, including molybdenum-carbide graphite (MoGr) and CuCD, with the goal of determining the material models to adopt in numerical simulations
Results show that, in spite of the energy density peak higher than what expected in the beam injection error (BIE) accident scenario, only minor scratches were produced on the thin films

Summary

Introduction

A novel design was proposed for LHC collimators [1], to cope with the requirements imposed by the High-Luminosity upgrade of the LHC (HL-LHC). During the first experiment, named “Jaws” [8], two full-scale HL-LHC collimator jaws in MoGr and CuCD were built, largely instrumented and installed in a vacuum chamber together with a standard LHC collimator in CFC Fig. 1. The test aimed at assessing the thermomechanical response under beam impact of the key elements such as absorbing blocks, taperings, BPMs and cooling circuit.

Results

Conclusion